Because of their excellent mechanical and electrical insulation properties, polymeric resin compositions are used in a broad range of applications such as in automotive parts, electrical and electronic parts, machine parts and the like. In many cases, because of the design flexibility they permit, sealing capability and their electrical insulation properties, polymer resin compositions can be used as encapsulants, housings and frames for electrical and electronics devices or motors. However, not only are electrical insulation properties needed in the encapsulating polymer compositions, but they also often need to have higher thermal conductivities especially with the downsizing trend of some electrical devices. Another important requirement for encapsulating polymer compositions is that their Coefficients of Linear Thermal Expansions (CLTEs) should be close to CLTEs of materials encapsulated with the polymer compositions to retain seal integrity while releasing heat generated by the encapsulated devices. In general, higher loading with thermally conductive filler in polymer leads to higher thermal conductivity and lower CLTE because the fillers' CLTEs are often lower than polymers' CLTEs. However, high filler loadings often decreases flow-ability of polymer compositions in melt forming processes, and that can lead to failure of sealing performance or damage of core devices encapsulated with the polymer compositions. Another important requirement for housings or frames is mechanical strength. Thus, polymer composition having higher thermal conductivity, electrically insulation, lower CLTE, higher mechanical strength and good flowability is desired.
Japanese patent application publication 2006-282783 discloses a polymer composition comprising polyarylene sulfide and fibrous filler and a moisture resistant magnesium oxide. However the composition's moisture resistance under high temperature and high pressure is not enough to be used under sever environment.
Japanese laid-open patent JP2008-1333382 discloses a polymer composition comprising liquid crystalline polymer and titanium oxide fiber and a moisture resistant magnesium oxide. However the composition's moisture resistance under high temperature and high pressure is not enough to be used under sever environment.